Elevators typically include a safety system to stop an elevator from traveling at excessive speeds in response to an elevator component breaking or otherwise becoming inoperative, or deviations from an intended motion profile due to motion control software errors. Traditionally, elevator safety systems include a mechanical speed sensing device commonly referred to as an overspeed governor, a governor rope, and a mechanical linkage connected to safety gear for selectively frictionally engaging elevator guiderails. The overspeed governor is traditionally mounted either in a machine room or in the top or bottom of the hoistway. The safety system is mounted on the car, and a linkage or governor rope hitch connects the system with the governor. When the governor detects a dangerous situation due to excessive travelling speed, it sends a force to the safety gear through the tensioned governor rope and linkage. The safety gear then engages the guiderails, and stops the elevator car.
A recent advance in elevator safety is the car mounted overspeed governor. By mounting the overspeed governor on elevator car, it can be directly linked to the safety gear also on the car, minimizing delays in activating the safety gear once an overspeed condition has been reached. In past elevator systems, where the overspeed governor is mounted at the top of the elevator shaft or in a machine room, the overspeed governor was linked through a linkage to the safety gear by connection to a rope, which sometimes caused delays in activating the safety gear after reaching an overspeed due to the length and elasticity of the rope. Additional benefits of the car mounted overspeed governor include a reduction in the amount of governor rope required (a single length of rope for an elevator car compared to an entire governor rope loop); the ability to install the governor at the factory, rather than in the field; and the reduction in complexity of safety linkages by eliminating the need for springs to resist the inertial forces of the governor rope loop during a sudden stop.